Sample preparation is an integral and perhaps the most important step in chemical analysis. A wide variety of samples of environmental, pharmaceutical, toxicological, biological, food, and clinical significance require simple, robust, and inexpensive alternative to current classical sample preparation technologies that are characterized with multi-step, laborious, expensive, and often unreliable results. One approach to sampling is directed to the use of surface-bonded hybrid organic-inorganic polymer coatings and monolithic beds for analytical microextraction. These systems display high chemical stability and offer a diverse array of extracting phases for solvent-free or solvent minimized analytical sample preparation. The availability of a wide variety of sol-gel precursors and sol-gel active organic macromers, oligomers, or dendrimers allow facile synthesis of advanced material systems with unique selectivity, enhanced extraction sensitivity and high thermal, mechanical and solvent stability. These sol-gel derived hybrid organic-inorganic advanced material systems have been shown to be effective in solvent free/solvent minimized sample preparation for a wide variety of analytes with biological, environmental, clinical, toxicological, food, pharmaceutical, bio-analytical, and forensic significance.
Sol-gel technology for the preparation of solid phase microextraction (SPME) sorbents has solved many limitations of conventional coatings. Sol-gel coatings chemically bond to different substrates, such as silica. Gel is formed from the sol solution in the presence of the substrate. Because of the wide variety of possible sol components, sol-gel technology allows the synthesis of a large number of sorbents for SPME and similar microextraction techniques (e.g., capillary microextraction, stir bar sorptive extraction) with large surface area, unique selectivity, and high thermal and solvent stability. Sol-gel monolithic beds are capable of achieving very high sample pre-concentration factors. The versatility of sol-gel technology allows the creation of surface-bonded sorbent coatings on unbreakable fiber materials (e.g., Ni—Ti, stainless steel, titanium, and copper) and also on substrates of different geometrical formats such as planar SPME (PSPME), and membrane SPME (MSPME). Sol-gel technology is adaptable to forming multi-component materials that have customized surface morphologies, selectivities, and affinities of the sorbent. A wide variety of sol-gel silica, titania, zirconia, alumina, and germania-based precursors are commercially available. Additionally, a wide range of sol-gel reactive organic ligands are available to design hybrid organic-inorganic sol-gel coatings that can be used to target a particular analyte or sample matrix with improved selectivity, sensitivity, extraction phase stability and performance.
There remains a strong need for solvent free or solvent minimized microextraction devices that permit the acquisition of low concentrations of analytes present in a wide range of aqueous or other liquid environments. Devices that can be used by untrained individuals to provide truly representative sample and allow the work up of these samples in a simple and effective manner are desirable.